Prevent product titles, descriptions & excerpts from being overwritten during Product Set updates

Here's the code you need to prevent customized product titles, excerpts and descriptions from being overwritten during a Product Set update. This is useful if you customize product titles or descriptions after the products are imported into your WooCommerce store.

By default, all fields (except the image field) are overwritten on update. To prevent data from being overwritten, action must be taken.